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APSnet featured image
Crazy top with abnormal tassel. Photograph courtesy
Mike Boehm Host (Latin and common name): Corn (Zea mays) Crazy top or downy mildew of corn is caused by the fungus Sclerophthora macrospora. The disease is widespread in the United States and has been reported in many countries around the world. Severe losses are seldom reported. Interestingly, S. macrospora also causes a disease on golf course turf called yellow tuft. Excessive soil moisture, irrigation or flooding is required for the development of both of these diseases. Both diseases are readily diagnosed by the presence of abnormal, excessive or seemingly uncontrolled growth or tillering such as that shown above. Such bizarre growth is believed to be the result of a hormonal imbalance brought about in the plant by the fungus. In the case of crazy top, the fungus survives in soil or in infected plant debris and becomes active with excessive soil moisture. Young plants (4-5 leaf stage) are extremely susceptible. Symptoms are highly variable depending upon many environmental and plant factors. Crazy top is managed through the avoidance of planting in low-lying wet spots or fields prone to flooding and by providing adequate soil drainage. APS publication number: IW000015 License to Copy. This notice hereby grants permission to APSnet
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